I’m experiencing this problem as well. There are far too many alien abductions. All it takes is for my Sim to have the misfortune of talking to an alien (and you can’t always tell who is an alien because they are disguised) for them to get abducted later on.
I played with a household of six Sims, one of whom was an alien. Every member of the household was abducted multiple times. Even after the alien left the household and died of old age, my vampire Sim who remained in the household was abducted another five times!
No member of the household was in the Scientist career.
Please, please add an option in the game settings to disable alien abductions.
No mods/No cc in my game.